1. Field of the Invention
The present invention relates to the use of amines and in particular to N (polyoxyalkyl)-N-(alkyl)amines to prepare elastomers and in particular those elastomers prepared via the reaction injection molded (RIM) and cast elastomer processes.
2. Prior Art
Current urethane technology offers potential end users a versatility unsurpassed by any other polymeric system. Using readily available intermediates and processing equipment, it is possible to prepare essentially solid polyurethanes ranging from very soft (40 Shore A) elastomers to very hard (80 Shore D) plastics. These polyurethanes have generally very good physical properties and as result large markets have evolved around their use.
Four major categories of intermediates are used in the preparation of typical urethane elastomer systems. These include: polyols, isocyanates, chain extenders and additives (including catalysts, fillers, internal mold releases and blowing agents).
Several classes of polyols have been used in the preparation of polyurethanes. These include polyesters, polycaprolactones, poly(1,4-butylene) oxides and polyoxyalkylene ethers based on propylene and ethylene oxides.
Amine terminated polyethers have been discussed in the literature for a number of years. These materials have the hydroxyl group of the conventional polyol replaced with a primary amine group using the well known reaction of ammonia with alcohols (polyols) under catalyzed high temperature conditions in the presence of hydrogen. A class of compounds prepared under these conditions is described in U.S. Pat. No. 3,654,370.
Recently, a high molecular weight material of the above class has been made commercially available and introduced into the marketplace. This material has a molecular weight of about 5000 and is prepared by the direct amination of a propylene oxide based triol with ammonia.
Independent of its high reactivity, this material has been used as the soft segment portion of several different high performance reaction injection molding (RIM) polyurea elastomers. While still very new in the RIM industry, these urea systems show considerable promise as candidates for high temperature resistant body panel applications in the automotive industry (i.e., paint oven temperatures of 195.degree.-205.degree. C.).
The major limitation that has restricted further growth of this type of material has been its very high reactivity. This high reactivity limits the shot size and thus part size using current RIM equipment. The problems with existing polyurea systems have been highlighted and a more processable polyurea RIM system is now required to further penetrate the potentially large automotive market.
U.S. Pat. No. 4,396,729 is the first patent indicating that it is possible to use a system comprising of an amine terminated polyether, an amine terminated chain extender, an aromatic isocyanate and an internal mold release in RIM. The patent primarily describes a RIM elastomer which will release from the mold without any external mold release, the system described uses an internal mold release.
U.S. Pat. No. 4,443,067 is the key patent describing an elastomer containing a major amount of polyurea linkages. The elastomer is prepared from an amine terminated polyether, an amine terminated chain extender and an aromatic isocyanate.
U.S. Pat. No. 4,444,910 is a modification of U.S. Pat. No. 4,443,067. It describes the addition of an organometallic catalyst to the RIM system. The addition of the catalyst helps the "green strength" of the elastomer although heat related properties were degraded.
U.S. Pat. No. 4,448,904 describes the use of high 2,4 isomer containing methylene bis(phenylisocyanate). Conventional RIM systems based on polyol require the use of high 4,4 isomer of MDI. The use of a polyether with greater than 50% amine end groups enables MDI containing greater than 10% of the 2,4 isomer to be used.
U.S. Pat. No. 4,474,900 describes the addition of an epoxy modified filler to an elastomer as described in U.S. Pat. Nos. 4,396,729, 4,444,910 and 4,443,067.
U.S. Pat. No. 4,474,901 describes the addition of low molecular weight (less than 1000) amine terminated polyethers to elastomers derived from polyethers of greater than 2500 molecular weight containing greater than 50% amine end groups, an amine terminated chain extender and an aromatic isocyanate.
U.S. Pat. No. 4,487,908 describes the addition of anhydrides to elastomers derived from polyethers of greater than 2500 molecular weight containing greater than 50% amine end groups, an amine terminated chain extender and an aromatic isocyanate.
U.S. Pat. No. 4,487,912 describes the addition of acid amides to elastomers derived from high molecular weight active hydrogen containing material, a chain extender and an aromatic isocyanate.
U.S. Pat. No. 4,499,254 describes the addition of a carboxylic acid of carbon number 10 or more to elastomers derived from polyethers of greater than 2500 molecular weight containing greater than 50% amine end groups, an amine terminated chain extender and an aromatic isocyanate.
U.S. Pat. No. 4,513,133 describes the addition of a low molecular weight organic acid to elastomers derived from polyethers of greater than 2500 molecular weight containing greater than 50% amine end groups, an amine terminated chain extender and an aromatic isocyanate.
U.S. Pat. No. 4,686,242 discloses elastomers made from an amine terminated polyether which is the reaction product of a polyether polyol and methyl amine. The patent further teaches that this approach actually produces an amine terminated polyether where the amine groups are predominantly primary amines.